5G Flexible Transceiver for Physical Layer Evaluation

Basic overview

The aim of this proposal is to extend the flexible PHY software component made available by the eWINE project with MIMO technologies. The goal is to utilize the second independent RF chain of the USRP SDR to employ Alamouti space-time coding (STC) combined with GFDM. This technique, firstly introduced for OFDM based wireless transmission systems, increases the reliability of the data transfer by transmitting multiply copies of the data stream. However, it has not yet been applied on the GFDM flexible waveform generation framework and, since GFDM is a nonorthogonal waveform, its combination with STC is not a straight forward approach.
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GFDM Library – How to use

In this library, only basic functions for GFDM transmission, signal generation, and naive reception are included, nothing fancy like channel estimation/equalization, iterative receivers, etc. The functions are grouped into several parts:

  • get_* These functions return objects that are commonly used for GFDM simulations.
  • calc_* These functions calculate (not only) performance values based on the passed objects.
  • do_* These more complex functions do actual simulation steps.

Remark: To use the library functions, you must include the library folder and subfolders to the MATLAB path.

The GFDM library has a folder with examples of use for the functions (GFDM_libraryexamples). With the purpose of illustration, an example file (GFDM_libraryexamplesser_in_awgn.m) for generation of a GFDM SER (Symbol Error Rate) curve is detailed below.

For the GFDM configuration, a parameter structure p contains the configuration of the GFDM system.

% GFDM configuration
p = get_defaultGFDM('BER');
p.pulse = 'rc_fd';
p.a = 0.5;

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GFDM Transmitter

  1. Create random data symbols
% create symbols
s = get_random_symbols(p);

The function get_random_symbols(p) returns a sequence of integers in range 0 ⋯ 2????−1 which are the transmitted data symbols.

  1. QAM-Modulate the symbols to QAM symbols and map the symbol stream to the data matrix
% map them to qam and to the D matrix
D = do_map(p, do_qammodulate(s, p.mu));

Map the integers in range 0 ⋯ 2????−1 to a quadratic QAM modulation using the MATLAB function qammod. The one-dimensional symbol stream is mapped to the data matrix D according to the values of ???????????????? and ????????????????. Empty sub-carriers and sub-symbols in D are set to zero. Afterwards there is the possibility to insert specific pilots or other information in the slots where no data is present.

  1. GFDM-Modulate the data matrix
x = do_modulate(p, D);

The matrix ???? is processed with the GFDM modulation scheme to produce a time domain signal with length ???????? that can be processed further. The transmitted signal is applied to an AWGN channel using the function do_channel. A channel object from MATLAB can be used as input parameter for this function for different channels.

% channel -> AWGN
xch = do_channel(x, 1, snr(si));% channel -> AWGN
xch = do_channel(x, 1, snr(si));

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Source: luciano@inatel.br

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5G physical layer specifications

The 5G specifications have been published as the 3GPP 38 series. Here we look at the physical layer specifications.

38.211: Physical channels and modulation

The scope is to establish the characteristics of the Layer-1 physical channels, generation of physical layer signals and modulation, and to specify:

  • Definition of the uplink and doecewnlink physical channels
  • Frame structure and physical resources
  • Modulation mapping (BPSK, QPSK, etc.)
  • OFDM signal generation
  • Scrambling, modulation and up-conversion
  • Layer mapping and precoding
  • Physical shared channel in uplink and downlink
  • Reference signal in uplink and downlink
  • Physical random-access channel
  • Primary and secondary synchronization signals

5G transmission numerologies

5G supports OFDM numerologies (μ) that can scale across the sub 6GHz to the mm-waves. The subcarrier scales from 15 KHz to 240 KHz (Δf).

Supported transmission numerologies in 5G (Credit: 3GPP TS 38.211 V15.1.0 Table 4.2–1)

The OFDM symbol duration and the cyclic prefix duration scale based on the numerology.

Scalable OFDM configuration (Credit: Ericsson)

The selection of numerology will depend upon the size of the cell and the frequency band. Large cells have a large time dispersion at the receiver. A large cyclic prefix needed to counter the larger time dispersion. Higher numerologies are preferable for higher frequencies as the wider subcarrier is less susceptible to phase noise.

Selecting the numerology based on cell size and frequency (cred: Ericsson)

Frames and subframes

Downlink and uplink transmissions are organized into frames into a 10ms frame as shown below:

Where:

The frame consists of 10 subframes of 1 ms each.

Slots

Just like LTE, a slot is always 14 symbols. The number of slots in a subframe depends on the numerology μ.

Number of OFDM symbols per slot, slots per frame, and slots per subframe for normal cyclic prefix. (Credit: 3GPP TS 38.211 V15.1.0 Table 4.3.2–1)

Symbol level TDD

5G slots support symbol level TDD formats. Each symbol can be designated as:

  • D: Downlink
  • U: Uplink
  • X: Flexible

UE assumes that downlink reception can take place only in symbols marked D or X in the following table.

Similarly, the UT can transmit in the uplink only in slots marked U or X.

Symbol level slot configuration (D: Downlink, U: Uplink, X: Flexible)

TS 38.212: Multiplexing and channel coding

The scope is to describe the transport channel and control channel data processing, including multiplexing, channel coding and interleaving, and to specify:

  • Channel coding schemes
  • Rate matching
  • Uplink transport channels and control information
  • Downlink transport channels and control information

Channel coding

5G NR traffic channels are encoded using the LDPC (Low Density Parity Check) coding. Control channels are encoded with the Polar codes.

Modulation schemes

5G-AN supports 1 to 8 bits per symbol (Q).

Downlink Control Channel (DCI) formats

A DCI transports downlink and uplink scheduling information, requests for aperiodic CQI reports, or uplink power control commands for one cell and one RNTI.

  • DCI format 0_0 is used for the scheduling of PUSCH in one cell.
  • DCI format 0_1 is used for the scheduling of PUSCH in one cell.
  • DCI format 1_0 is used for the scheduling of PDSCH in one DL cell.
  • DCI format 1_1 is used for the scheduling of PDSCH in one cell.
  • DCI format 2_0 is used for notifying the slot format.
  • DCI format 2_1 is used for notifying the PRB(s) and OFDM symbol(s) where UE may assume no transmission is intended for the UE.
  • DCI format 2_2 is used for the transmission of TPC commands for PUCCH and PUSCH.
  • DCI format 2_3 is used for the transmission of a group of TPC commands for SRS transmissions by one or more UEs. Along with a TPC command, a SRS request may also be transmitted.

TS 38.213: Physical layer procedures for control

The scope is to establish the characteristics of the physical layer procedures for control, and to specify:

  • Synchronization procedures
  • Uplink power control
  • Random access procedure
  • UE procedure for reporting control information
  • UE procedure for receiving control information

Cell search and timing adjustment

The cell search and timing adjustment procedures have been enhanced to work for 15 KHz to 240 KHz subcarrier spacing.

Power control

The power control scheme has also been extended to work for all numerologies. The 2^μ term in the PUSCH power calculation factors in the different numerologies.

TS 38.214: Physical layer procedures for data

The scope is to establish the characteristics of the physical layer procedures for data, and to specify:

  • Power control
  • Physical downlink shared channel related procedures
  • Physical uplink shared channel related procedure

Downlink MCS index table

The downlink MCS index table specifies the modulation, coding and the overall spectral efficiency of the PDSCH.

MCS index table for PDSCH

Uplink MCS index table

The uplink MCS index table specifies the modulation, coding and the overall spectral efficiency of the PUSCH.

MCS index table for PUSCH

Downlink CQI reporting

The UE reports downlink CQI via a 4-bit field that is carried over the PUCCH or the PUSCH. Two different tables are defined.

  • CQI reporting limited to 64-QAM
CQI reporting table (limited to 64-QAM)
  • CQI reporting extended to 256-QAM
CQI reporting table (extended to 256-QAM)

TS 38.215: Physical layer measurements

The scope is to establish the characteristics of the physical layer measurements, and to specify:

  • Control of UE/NG-RAN measurements
  • Measurement capabilities for NR

5G NR physical layer introduction

The following video provides a good overview of the 5G NR physical layer. The topics covered are:

Waveforms and frame structure

  • Scalable numerology
  • Numerology multiplexing
  • Dynamic TDD

Millimeter waves

  • Beam sweeping
  • Beam management
  • Massive MIMO

Low latency

  • Mini slots
  • CBG (code block group) retransmission
  • Front loaded DMRS (demodulation reference signal)
Understanding the 5G NR physical layer (slides)

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5G New Radio Self-introduction

3GPP

http://www.3gpp.org/

What is the 3GPP standard 5G why organizations cannot do without it? 
Time flies, blink of an eye to 2017, from its inception in 1998, 3GPP continues to expand, driven by the members, involve a lot of work and hundreds of companies Collaboration, including network operators, terminal manufacturers, chip manufacturers, infrastructure manufacturers, academia, research institutions, government agencies, accumulated to more than 6,000 participants in 2017, good guys, great. 
http://news.mydrivers.com/1/562/562043.htm

access network and core network

Evolution from 3G to 4G, the access network and the core network “integrated” to the 4G era. 
to 5G is not the same, 3GPP organization to access network (5G NR) and core network (5G Core) apart, to independently evolve to 5G era.

4G wireless access is called eLTE, and 5G base station wireless access is called New Radio, abbreviated NR. 
5G, in the first stage, eLTE will follow with NR and the common 4G core network. Then the network evolves slowly and NR will access its own core network, which may happen in the second phase of 5G.

5G 3 scenes

  1. eMBB (Enhanced Mobile Broadband): Enhanced mobile broadband (bands below 6 GHz)
  2. URLLC (Ultra-Reliable Low-Latency Communications): Ultra-reliable low-latency communication (bands below 6 GHz), such as unmanned services.
  3. mMTC (massive Machine Type Communications): Large-scale machine communication/large-scale Internet of Things (under 6 GHz band)

Note that these three terms will be widely used in future communications.

5G NR

3G base stations called the NodeB (NB) 
4G base station called the eNB (Enhanced NB)

What is the 5G base station called? 
3GPP give it a name, GNB

The wireless access of the 5G base station is called New Radio, abbreviated NR

5G NR’s “self-introduction” http://www.eefocus.com/communication/408007

LDPC/Polar

I don’t know if my friends can remember that in late November 2017, Huawei’s main (Polarization Code) scheme won 5G as the control scheme for the control channel. The eMBB scenario of one of the three scenarios developed by 3PGG , and the Qualcomm-led LDPC code is used as the coding scheme for the data channel.

According to Huawei’s actual test, the Polar code can meet the requirements of ultra-high-rate, low-latency, and large-connection scenarios, and can increase the spectrum of the cellular network by about 10%, and combine with millimeter waves to achieve 27Gbps. rate.

For the eMBB scenario, with Huawei’s main force, plus Qualcomm’s support, I believe that wireless communication technology can be upgraded to a new height.

4G mobile communication network architecture

the UE (User Equipment) 
E-the UTRAN (Access Network) 
the EPC (Core Network)

the MME: Mobility Management the Entity 
S-GW: the Serving the GateWay, serving gateway 
P-GW: the PDN the GateWay, the PDN gateway 
E-the UTRAN: Evolved Universal Terrestrial Radio Access the Network 
the EPC: Evlved packet core evolved packet core 
the RRC: radio refers to the resource control RRC
the PDCP: packet the data convergence protocol packet data convergence protocol 
the RLC: radio link control RLC layer protocol 
PHY: Physical Layer Protocol

User and Control Surfaces

https://blog.csdn.net/wowricky/article/details/6907715
go user plane data 
go control plane signaling

eNodeB function

includes physical layer functions (HARQ, etc.), MAC, RRC, scheduling, radio access control, mobility management.

gateway

Everyone knows that going from one room to another is bound to go through a door. Similarly, sending information from one network to another must also go through a “gateway”, which is the gateway. As the name suggests, a gateway is a “gateway” in which a network connects to another network.

Assuming your name is small (small), you live in a large yard, your neighbor has many small partners, and your parents are your gateway. When you want to play with a little friend in the yard, as long as you yell at his name in the yard, he will respond to you when he hears, and run out to play with you.

But your parents don’t allow you to get out of the door. Everything you want to do with the outside world must be contacted by your parents (gateway) to help you. If you want to chat with your classmate Xiao Ming, Xiao Ming’s family lives in another yard far away. He also has parents at home (Xiao Ming’s gateway). But you don’t know the phone number of Xiao Ming’s home, but your class teacher has a list of all the classmates in your class and a phone number comparison table. Your teacher is your DNS server. So you have the following conversation with your parents at home:

Small point: Mom (or Dad), I want to find the class teacher to check Xiaoming’s phone number line? 
parents: Well, you wait. (Then your parents hang a phone call to your class teacher and ask Xiao Ming’s phone.) Asked, his home number is 211.99.99.99 Little is not too good: great! Mom (or dad), I want to find Xiao Ming, you can contact me for Xiao Ming. 
parents: no problem. (Then the parent sent a request to the telephone office to call Xiaoming’s phone. The last level was of course transferred to the Xiaoming’s parents, and then his parents transferred the call to Xiaoming)

So you got in touch with Xiao Ming.

If you figure out what a gateway is, the default gateway is well understood. Just like a room can have multiple doors, a host can have multiple gateways. The default gateway means that if a host cannot find an available gateway, it will send the packet to the default gateway, which will process the packet. Default gateway. The default gateway is usually filled in 192.168.x.1

retransmission mechanism

ARQ and HARQ 
HARQ: Hybrid Automatic Repeat reQuest (HARQ) https://www.jianshu.com/p/f8650640660b

BBU and RRU

RRU is the Remote Radio Unit remote radio module, and the BBU is the Building Baseband Unit indoor baseband processing unit.

The baseband BBU is placed in the equipment room in a centralized manner. The RRU can be installed to the floor. The BBU and the RRU are connected by optical fiber. The RRU is connected to the antenna through a coaxial cable and a power splitter (coupler), that is, the trunk uses optical fiber. The road uses coaxial cable.

For the downlink direction: the optical fiber is directly connected to the RRU from the BBU, and the baseband digital signal is transmitted between the BBU and the RRU, so that the base station can control a certain user’s signal to be transmitted from the designated RRU channel, which can greatly reduce the local cell. User interference on other channels. 
For the uplink: the user’s phone signal is received from the nearest channel, and then transmitted to the base station through an optical fiber from the channel, this also can greatly reduce the interference between users on different channels.

Active and passive antennas

Passive Antenna: It is purely a metal body and is a variety of antennas that are commonly seen. 
active antenna: this is the normal antenna and amplifier is to improve sensitivity and to reduce signal noise.

GPS antenna using the difference between active and passive 
http://www.arsgps.com/ Changjianwenti/30-80.html

QoS

IP address

The so-called IP address is a 32bit address assigned to each host connected to the Internet . According to the TCP/IP protocol, the IP address is expressed in binary. Each IP address is 32 bits long, and the bit is converted into bytes, which is 4 bytes. For example, an IP address in binary form is “00001010000000000000000000000001”. With such a long address, people are too hard to handle. In order to facilitate people’s use, IP addresses are often written as ” strong” in decimal form, and different characters are separated by the symbol “.” in the middle. Thus, the above IP address can be expressed as “10.0.0.1”. This representation of the IP address is called “ dotted decimal notation“, which is obviously much easier to remember than 1 and 0.

Each IP address contains two parts: Network ID and Host ID. Every computer on the entire Internet is identified by its own unique IP address. IP addresses form the basis of the entire Internet, and it is so important that each networked computer does not have the right to set its own IP address. There is a unified agency (IANA) that assigns a unique network ID to the organization of the application. The application organization can assign a unique host ID to each host in its network, just as a unit does not have the right to determine the street name and house number of the city in which it belongs, but can independently determine the individual office numbers within the unit.

According to the different number of digits of the network ID and host ID, the IP address can be divided into A (7-bit network ID and 24-bit host ID), B (14-bit network ID and 16-bit host ID), C (21) There are three types of bit network IDs and 8-bit host IDs. Due to historical reasons and differences in technology development, Class A addresses and Class B addresses are almost completely depleted. Currently, only Class C addresses can be allocated to organizations in various countries around the world. So IP address is a very important network resource.

The IP address and subnet mask are combined to obtain the network ID and host ID.

For an organization that has set up an Internet service, because its host has opened access services such as WWW, FTP, E-mail, etc., it usually publishes a fixed IP address to facilitate user access. Of course, digital IP is inconvenient to remember and recognize. People are more accustomed to accessing a host through a domain name, and the domain name actually needs to be translated into an IP address by a domain name server (DNS). For example, your home page address is www.myhost.com , which users can easily remember and use, and the domain name server translates the domain name into 101.12.123.234, this is your real address on the Internet.

For most dial-up users, it is highly undesirable to assign a fixed IP address (static IP) to each user due to the discrete time and space of the Internet. This will result in a huge IP address resource. waste. Therefore, these users usually get a dynamic IP address every time they dial the ISP’s host . This address is of course not arbitrary, but the network ID and host ID of the ISP are legal. An address in the interval. The IP address of the dial-up user when connecting twice is likely to be different, but the IP address does not change during each connection time.

5G NR spectrum

http://www.eefocus.com/communication/408007/p3

In the R15 version, two major FRs (frequency ranges) are defined:

LTE band number starts with B, such as LTE B20 (Band 20) The 5G NR band number identifier starts with n, and the 20th band in the 5G NR is called n20.

http://www.sharetechnote.com/html/5G/5G_FR_Bandwidth.html#Operating_Band

FDD/TDD/SDL/SUL

https://zhidao.baidu.com/question/91344791.html

  1. TDD means time division duplex. ( refers to the duplex mode) TDDUses time to separate the receive and transmit channels. In the TDD mobile communication system, different time slots using the same frequency carrier are received and transmitted as bearers of the channel, and time resources are allocated in two directions. The base station sends a signal to the mobile station during a certain period of time, and the time interval in the middle is sent by the mobile station to the base station, and the base station and the mobile station must cooperate in order to work smoothly.
  2. FDD means frequency division duplex. ( refers to the duplex mode, and the transceiver uses different frequencies.) FDD is used to receive and transmit on two separate symmetric frequency channels, and the guard band is used to separate the receiving and transmitting channels. The disadvantage of FDD is that it must use pairs of frequencies, relying on frequency to distinguish between uplink and downlink, and its unidirectional resources are continuous in time.
  3. SDL can only be used for downstream transmissions
  4. SUL can only be used for upstream transmissions
  1. Frequency Division Duplex Bands (FDD)
  2. Time Division Duplex Bands (TDD)
  3. Supplementary Bands: Supplementary Downlink Bands (SDL)
  4. Supplementary Bands: Supplementary Uplink Bands (SUL)

PAPR

https://baike.baidu.com/item/PAPR/5310514?fr=aladdin

Peak to Average Power Ratio (PAPR), referred to as peak-to-average ratio (PAPR).

The

MIMO-OFDM system provides greater coverage, better transmission quality, higher data rates, and spectral efficiency.

However, since the OFDM symbol is superposed by a plurality of independently modulated subcarrier signals, when the respective subcarriers have the same phase or similar , the superimposed signal is subjected to the same initial phase signal. The modulation, which produces a large instantaneous power peak, further leads to a higher peak-to-average power ratio (PAPR), referred to as peak-to-average ratio (PAPR).

Because the dynamic range of the general power amplifier is limited , the MIMO-OFDM signal with a relatively large peak is easy to enter the nonlinear region of the power amplifier, This causes the signal to produce nonlinear distortion, resulting in significant spectral spread interference and in-band signal distortion, resulting in severe degradation of overall system performance. The peak-to-average ratio has become a major technical obstacle to MIMO-OFDM.

Carrier Aggregation

Carrier Aggregation (CA) is to synthesize a fragmented LTE band into a wider frequency band of “virtual” to meet the certain preconditions to increase the data rate.

Carrier aggregation can use continuous bandwidth and discontinuous bandwidth, and bandwidth flexibility is great. A single carrier in carrier aggregation is called a CC (component carrier), and each CC can use any bandwidth (1.4, 3, 5, 10, 15, and 20 MHz) specified by LTE R8.

Physical layer of 5G-NR

http://www.eefocus.com/communication/408007/p4

OFDM symbol duration and number of subcarriers

  1. The duration of the OFDM symbol depends on the spacing of the subcarriers and the length of the CP.
  2. When the subcarrier spacing is constant, the number of subcarriers depends on the channel bandwidth. The number of subcarriers does not affect the duration of the OFDM symbol.
  3. When the channel bandwidth is constant, the subcarrier spacing is small, and more subcarriers can be placed, but the OFDM Symbol Duration becomes longer and the data transmission rate does not change. (The modulation is the same regardless of CP and other overhead, and the subcarriers fill the channel bandwidth).

For example, Let OFDM Symbol Duration be 1ms, the subcarrier spacing is 1kHz, when the channel bandwidth is 10kHz, 10 subcarriers can be placed. If the modulation is BPSK, the data transmission rate is 10×1bit/1ms=10kbps. If the subcarrier spacing becomes 0.5 kHz, 20 subcarriers can be placed, and the data transmission rate at this time is 20 × 1 bit / 2 ms = 10 kbps.

Visible, the highest transmission rate of an OFDM waveform is:

Waveform waveform

Currently 3GPP Release 15 has determined that CP-OFDM supports 5G NR uplink and downlink, and also introduces DFT-S-OFDM waveforms complementary to CP-OFDM waveforms. CP-OFDM waveforms can be used for single-stream and multi-stream (ie, MIMO) transmissions, while DFT-S-OFDM waveforms are limited to single-stream transmissions with limited link budget constraints.

Waveform (for eMBB/URLLC and <52.6 GHz) • DL Waveform: CP-OFDM • UL Waveform: CP-OFDM + DFT-s-OFDM

CP-OFDM targeted at high throughput scenarios DFT-s-OFDM targeted at power limited scenarios

Understanding the 5G NR Physical Layer

Multiple Access Multiple Access Scheme

  • Orthogonal Multiple Access
  • Non-Orthogonal Multiple Access (NOMA) not supported in Rel-15

physical channel bandwidth

http://www.eefocus.com/communication/408007/p5

In the frequency band less than 6 GHz (FR1), the maximum channel bandwidth of 5G NR is 100 MHz 
in the millimeter wave band (FR2), and the maximum channel bandwidth of 5G NR is 400 MHz, which is much larger than the maximum channel bandwidth of LTE of 20 MHz.

But it is worth mentioning that the bandwidth utilization of 5G NR has increased significantly to over 97% (LTE bandwidth utilization is only 90%). 
How to understand 5G NR enhance bandwidth utilization?

The

10 MHz 4G channel has 50 RBs, each RB has 12 subcarriers, and the 10 MHz 4G channel has a total of 600 subcarriers. Since each subcarrier has an interval of 15 kHz, 15*600 is equal to 9000 kHz or 9 MHz, which means that only 9 MHz is utilized in the 10 Mhz channel, and about 1 MHz is left as the guard band, so the bandwidth utilization of LTE is only 90. %. By analogy, a 20MHz 4G channel has 100 RBs, which uses only 18MHz in a 20MHz bandwidth; a 50MHz 4G channel has 250 RBs…

Guess what is the number of RBs in a 50MHz 5G channel? 275. (270×12×15e3)/50e6 = 99%

Numerology

Numerology This concept can be translated into a parameter set, which roughly means a set of parameters, including subcarrier spacing, symbol length, CP length, and so on. http://www.eefocus.com/communication/408007/p4

Scalable subcarrier spacing

The subcarrier spacing is a trade-off between the symbol duration and the CP overhead: the smaller the subcarrier spacing, the longer the symbol time length; the larger the subcarrier spacing, the larger the CP overhead.

5G NR The most basic subcarrier spacing is the same as LTE, it is also 15kHz, but it can be flexibly extended

Understanding the 5G NR Physical Layer

TTI (Time Transmission Interval)

Qualcomm reference page 
https://www.qualcomm.com / Invention / Technologies / NR-5g / Unified-AIR-interface 
HTTPS: // WWW .eetimes.com/document.asp?doc_id=1278199

frame structure

http://www.sharetechnote.com/html/5G/5G_FrameStructure.html http://www.eefocus.com/communication/408007/p5

The length of the 5G radio frame and the subframe are fixed. The length of one radio frame is fixed to 10ms, and the length of one subframe is fixed to 1ms. This is the same as LTE, so as to better maintain the coexistence between LTE and NR, which facilitates synchronization of time slot and frame structure in the joint deployment mode of LTE and NR, and simplifies cell search and frequency measurement.

The difference between

is that the 5G NR defines a flexible sub-architecture, and the slot and character length can be flexibly defined according to the subcarrier spacing.

Therefore, we simply divide the 5G frame structure into two parts: a fixed structure and a flexible structure (see figure).

This is like building a house. The frame structure is fixed, and the space inside can be flexibly arranged according to your needs.

Understanding the 5G NR Physical Layer

Resource Block

Resource Block (RB) Physical Resource Blocks (PRB) http://niviuk.free.fr/store_fiveg.php

Basic Concepts of LTE Resource Blocks

  • RE (Resource Element): The minimum granularity of physical layer resources. Time domain: 1 OFDM symbol, frequency domain: 1 subcarrier
  • RB (Resource Block) The resource allocation frequency domain minimum unit of the physical layer data transmission . Time domain: 1 slot, frequency domain: 12 consecutive subcarriers (Subcarrier)
  • TTI: time-domain basic unit of physical layer data transmission scheduling 1 TTI = 1 subframe = 2 slots 1 TTI = 14 OFDM symbols (Normal CP) 1 TTI = 12 OFDM symbols (Extended CP)

Resource Grid

Understanding the 5G NR Physical Layer

  • Resource elements are grouped into Physical Resource Blocks (PRB) – Each PRB consists of 12 subcarriers

http://www.sharetechnote.com/html/5G/5G_FrameStructure.html#Resource_Grid

☆ http://niviuk.free.fr/lte_resource_grid.html ☆

Slot

Slot Structure

Understanding the 5G NR Physical Layer

Slot Format

http://www.sharetechnote.com/html/5G/5G_FrameStructure.html#Slot_Format (Note # and the following section, you can link to a section of the page)

http://www.sharetechnote.com/html/5G/5G_FrameStructure.html#Resource_Grid

channel coding

5G NR data channel adopts LDPC code instead of LTE Turbo code; 5G NR broadcast channel and control channel adopt Polar code instead of LTE TBCC code.

Why does the data channel replace the Turbo code with an LDPC code?

Turbo code is characterized by low coding complexity, but high decoding complexity , and LDPC code is just the opposite . Considering that in the eMBB scenario, the code block is greater than 10000 and the code rate is up to 8/9, which is a serious injury to the Turbo code with high decoding complexity, and the decoding algorithm of LDPC is relatively simple and practical, just right.

It’s like having a song, just meeting you.

In addition, the use of LDPC essentially parallel processing mode, and the Turbo code is essentially serial and therefore LDPC scheme is applicable to low-delay applications .

As for the Polar code, although it is late, it has the characteristics of low coding and decoding complexity, and is very flexible. It has good performance at any code length and bit rate, and certainly becomes the control channel. Second choice.

Initial access and beam management

Understanding the 5G NR Physical Layer

Physical Channels and Signals

SS Block SS Burst SS Burst Set

5G/NR – Synchronization

http://www.sharetechnote.com/html/5G/5G_Phy_Synchronization.html

NR Synchronization Process

When we say ‘ Synchronization ‘ in communication technology, it usually mean ‘ synchronization for transmission ‘ and 39; synchronization for reception ‘ .

In UE ‘ s point of view, ‘ transmitting direction ‘ is called ‘ Uplink ‘ and ‘ receiving direction ‘ is called 39; Downlink & # 39; . the Applying the this Terms to Synchronization Process, WE have have TWO types of Synchronization in Cellular Communication Including. 5G / NR Called & # 39; Downlink Synchronization & # 39; and & # 39 ; Uplink Synchronization‘ .

Donwlink Synchronization: This is the process in which UE detect the radio boundary (ie, the exact timing when a radio frame starts) and OFDM symbo boundary (ie, the exact timing when an OFDM symbol starts). This process is done By detecting and analyzing SS Block. This is a pretty complicated process and follow through SS Block Page for the detailed Understanding.

Uplink Synchronization: This is the process in which UE figure out the exact timing when it should send uplink data (ie, PUSCH / PUCCH). Usually a network (gNB) is handling multiple UEs and the network has to ensure that the Uplink signal from every UE should be aligned with a common receiver timer of the network. So this involves much more complicated process and sometimes it has to adjust UE Tx timing (uplink timing) of each UE. This is called RACH process. Of course, you need to go through much longer pages of reading. Read through RACH pagefor the details.

Overal Procedure of Synchronization and Initial Access

Overal Procedure of Synchronization and Initial Access
when we just say ” Synchronization ” , usually mean Downlink Synchronization. Of course, Uplink Synchronization is very important as well, but usually the uplink process is pursue as part of RACH process and normaly treated under ” RACH Procedure ” or ” Initial Access ” process .

How Synchronization work ?

The most common way to implement the Synchronization is

i) Create a predetermined signal (a predefined data sequence : This signal is called Sync signal) 
ii) Put the signal into a specific OFDMA symbol in a specific subframe and transmit

Since UE already have (or can derive) all the details of the predetermined sync signal, it can search and detect the data from the stream of data reaching the UE. Because the sync signal is located in the predefined location in time, UE can detect the exact timing from the decoded sync signal.

What kind of Information can be derived from the Synchronizaiton Signal ?

What kind of Information can be derived from the Synchronizaiton Signal ?

Synchronization Signal in Frame Structure

Synchronization Signal in Frame Structure

the order of modulation

Modulation Order

Wikipedia The modulation order of a digital communication scheme is determined by the number of the different symbols that can be transmitted using it.

  1. BPSK: The simplest forms of digital modulation are of second order because they can transmit only two symbols (usually stated as as ” 0 ” and ” 1 ” ).
  2. QPSK: 4th order modulation
  3. 16QAM: 16th order modulation

modulation order can be used to calculate the number of bits each modulation symbol can represent, log2 (modulation order) = n bit / symbol

LTE random access

Random access is essentially implementing uplink synchronization between the terminal and the base station, which is the air interface level. The essence of the attachment is to allow the terminal to successfully access the core network and successfully obtain the IP address, which is at the core network level.

http://www.sharetechnote.com/html/RACH_LTE.html

  • RACH stands for Random Access Channel.
  • This is the first message from UE to eNB when you power it on.
  • In terms of eNB point of view, it would seem that it is getting this initial UE signal in almost random fashion (eg, in Random timing , Random Frequency and in Random Identification) because it has no idea when a user turn on The UE (Actually it is not completely random, there are a certain range of agreement between UE and Network about the timing, frequency location and possible indentification, but in large scale it would look like working in random fashion).

Why RACH ? (Why RACH is required)

The main purpose of RACH can be described as follows. i) Achieve UP link synchronization between UE and eNB Ii) Obtain the resource for Message 3 (eg, RRC Connection Request)

In most of the communication (especially digital comunication regardless of whether it is wired or wireless), the most important precondition is to establish the timing synchronization between the reciever and transmitter. So whatever communication technology you Would study, you would see some kind of synchronization mechanism that is specially designed for the specific communication.

synchronization in downlink: In LTE, the synchronization in downlink (Transmitter = eNB, Reciever = UE), this synchronization is achieved by the special synchronization channel (special physical signal pattern). Refer to Time Sync Process page for the details. This downlink sync signal gets broadcasted to everybody and it Is get transmitted all the time with a certain interval.

synchronization in uplink: However in Uplink(Transmitter = UE, Reciever = eNB), it is not efficient (actually waste of energy and causing a lot of interference to other UEs) if UE is using This kind of broadcasting/always-on synchronization mechanism. In case of uplink, this synchronization process should meet the following criteria i) The synchronization process should happen only when there is immediate Ii) The synchronization should be dedicated to only a specific UE All the complicated/confusing stories in this page is mostly about the process specially designed mechanism to meet these criteria.

Another purpose of RACH process is to obtain the resource for Msg3 (Message 3). RRC Connection Request is one example of Msg3 and there are several different types of Msg3 depending on situation.

Two types of RACH process

(http://www.sharetechnote.com/html/RACH_LTE.html#Two_types_of_RACH_process) 
Two types of the RACH Process: Contention-based and Contention-Free

RACH Process Overview In Diagrams

http://www.sharetechnote.com/html/RACH_LTE.html#RACH_Process_Overview_In_Diagrams

CRC

CRC is the Cyclic Redundancy Check (Cyclic Redundancy Check): It is the most commonly used error checking code in the field of data communication, and its feature is that the length of the information field and the check field can be arbitrarily selected. Cyclic Redundancy Check (CRC) is a data transmission error detection function that performs polynomial calculation on data and attaches the result to the back of the frame. The receiving device also performs a similar algorithm to ensure the correctness and completeness of the data transmission. Sex.

https://blog.csdn.net/weicao1990/article/details/51669853
http://www.sharetechnote.com/html/Handbook_Communication_CRC.html

terminology

physical channel and physical signal

physical channels: A collection of a series of resource elements (RE: Resource Elements) for carrying information from higher layers. 
physical signals (Signals PHYSICAL) : RE corresponding to a series of physical layer, but do not pass any information RE from the top. Such as reference signal (RS), synchronization signal. RS (Reference Signal): reference signal, also commonly referred to as pilot signal; SCH (PSCH, SSCH): synchronization signal, divided into primary synchronization signal and secondary synchronization signal.

logical channel and transport channel

logical channel (the Logical Channel) 
transport channels (Transport Channe) 
HTTP: //www.techplayon. Com/2411-2/
https://www.tutorialspoint.com/lte/lte_communication_channels.htm 
http://www.rfwireless-world.com/Tutorials/LTE-logical-transport-physical-channels.html

LTE sync signal

CSI

CSI (Channel State Information ) : Channel state information

https://blog.csdn.net/m_052148/article/details/72824979
In LTE, we usually refer to Channel State Information (CSI), which mainly includes PMI, RI, and CQI. PMI means a precoding matrix, and the UE informs the eNB of the best precoding matrix for the current DL-SCH transmission through the PMI. RI is the meaning of the rank indication, telling the eNB the optimal number of layers for the current DL-SCH transmission. CQI is a channel quality indicator, indicating that after the recommended RI and PMI are adopted, to ensure that the error rate of downlink DL-SCH reception does not exceed 10%, the highest modulation coding scheme available, that is, the value of CQI will affect the downlink. The value of MCS.

What is CSI

http://www.sharetechnote.com/html/Handbook_LTE_CSI.html#What_is_CSI

CSI is a kind of collective name of several different type of indicators (UE report) as listed below.

  • Channel Quality Indicator(CQI)
  • precoding matrix indicator (PMI)
  • precoding type indicator (PTI)
  • rank indication (RI)

Layer mapping and precoding

layer mapping

http://www.sharetechnote.com/html/PhyProcessing_LTE.html
http://www.sharetechnote.com/html/BasicProcedure_LTE_PHY_Precoding.html
https: //blog.csdn .Net/zhihuiyu123/article/details/81461189
https://blog.csdn.net/cun_yun/article/details/45580965
https://blog.csdn.net/zhihuiyu123/article/details/79264513
http://blog.sina.com.cn/s/blog_65a28d8a0102x9g1.html
https://link.springer.com/content/pdf/10.1155/2009/302092.pdf

In LTE, in the spatial multiplexing mode, the number of layers is equal to the rank of the channel matrix, that is, the number of data streams that can be independently transmitted in parallel. https://communities.theiet.org/blogs/426/430
There are mainly Two types of layer mapping: one for spatial multiplexing and the other for transmit diversity.

  • In case of spatial multiplexing, there may be one or two code-words. But the number of layers is restricted. On one hand, it should be equal to or more than the number of codewords On the other hand, the number of layers cannot exceed the number of antenna ports. The most important concept is ‘layer’. The layers in spatial multiplexing have the same meaning as ‘streams’. They are used to transmit multiple data streams in In parallel multiplexing, the number of layers may be adapted to the transmission rank, by means of the feedback of a Rank Indicator (RI) to the layer mapping.
  • In case of transmit diversity, there is only one codeword and the number of layers is equal to the number of antenna ports. The number of layers in this case is not related to the transmission rank, because transmit-diversity schemes are always single-rank transmission schemes. The layers in transmit diversity are used to leisure carry out the following precoding by some pre-defined matrices.

MIMO in LTE and LTE-Advanced

precoding

http://rfmw.em.keysight.com /wireless/helpfiles/89600b/webhelp/subsystems/lte/content/lte_overview.htm 
https://www.mathworks.com/help/lte/examples/lte-dl-sch-and-pdsch-processing-chain.html

space diversity VS spatial multiplexing

transmit diversity VS beamforming

LTE MIMO modes

https://www.radio-electronics.com /info/cellulartelecomms/lte-long-term-evolution/lte-mimo.php 
HTTP: / /www.sharetechnote.com/html/BasicProcedure_LTE_MIMO.html

sharetechnote

☆ http://www.sharetechnote.com/ ☆

5G NR physical layer

5G physical layer specifications
5G New Radio: Unveiling the Essentials of the Next Generation Wireless Access Technology
New Radio. 5G – Unveiling The Essentials of the Next Generation The Wireless Access Technology (local file)

Subcarrier spacing, CP length, and the number of slots per subframe are controlled by same parameter. \(\mu (0,1,2,3,4)\)

Subcarrier spacing: \(2^\mu\cdot 15kHz\)
CP duration: \(2^{-\mu}\cdot 4.7{\mu}s\)
Each per subframe Number of time slots: \(2^\mu \)

Each slot contains 14 OFDM symbols. 
one resource block includes 12 consecutive subcarriers. (A resource block (RB) consists of 12 consecutive subcarriers in the frequency domain.)

SSB

The combination of SS and PBCH is referred to as SSB in NR.
NR SS consists of primary SS (PSS) and secondary SS (SSS).

By detecting SS, a UE can

PHYSICAL Obtain The Cell Identity, 
Achieve both in Downlink Synchronization Time and Frequency Domain, 
The Acquire and Timing for the PBCH. Carries the PBCH Very The Basic System Information.

The starting point of the physical layer is the transport block (TB: Transport Block) transmitted from the MAC layer, and the end point is to generate the baseband OFDM signal. The up-converting or down-converting then converts the baseband OFDM signal into a radio frequency signal and transmits it through the antenna. 
the TB (transport block) is the basic unit of data exchanged between the MAC layer and a physical layer for physical layer processing. The physical layer adds CRC check information to each TB. 
. 5G New Radio: The Essentials Unveiling of the Next Generation The Wireless Access Technology

frame structure

SFN
SFN System Frame Number System Frame Number 
Used in LTE The 10 bit carries the data, is carried in the MIB, and is transmitted in the PBCH. The SFN bit length is 10 bits, which means that the value is from 0-1023 cycles. In the MIB broadcast of the PBCH, only the first 8 bits are broadcast, and the remaining two bits are determined according to the position of the frame in the PBCH 40 ms period window, the first 10 ms frame is 00, the second frame is 01, and the third frame is 10, Four frames are 11. The PBCH 40ms window phone can be determined by blind detection.

LTE physical transmission resources (1) – frame structure and OFDM symbols
3.TDD Frame structure 
The frame structure mode of the LTE-TDD protocol is generally referred to as Frame structure type 2, and is referred to herein as a TDD frame structure for the sake of clarity. 
In TDD, the length of each radio frame is Tf=10ms, which consists of two “ fields ”, each “half frame” has a length equal to 5ms, consisting of 5 consecutive children. Frame composition, each sub-frame length is equal to 1ms.

When the same subframe is in different uplink-downlink configurations, data in different directions may be sent. The following figure shows the direction in which all subframes send data under various uplink and downlink subframe configurations. D indicates that the subframe can only send downlink data, U indicates that the subframe can only send uplink data, and S indicates a special subframe, which is generally used for downlink data transmission.

downlink – uplink handover period (Downlink-Uplink Switch-to-Point periodicity) 
downlink – uplink handover within a 10ms period and the number of related special subframe , calculated with reference to the FIG. .

 

 

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,

Link Level (LL) Simulation vs System Level (SL) Simulation

In the development and standardization of LTE, as well as in the implementation process of equipment manufacturers, simulations are necessary to test and optimize algorithms and procedures. This has to be carried out on the physical layer (link level) and in the network (system level) context:

Link level simulations
LL simulations allow for the investigation of channel estimation, tracking, and prediction algorithms, synchronization algorithms, Multiple-Input Multiple-Output (MIMO) gains, Adaptive Modulation and Coding (AMC) and feedback. Furthermore, receiver structures (typically neglecting inter-cell interference and impact of scheduling, as this increases simulation complexity and runtime dramatically), modelling of channel encoding and decoding, physical layer modelling crucial for system level simulations and alike are typically analyzed on link level. Although MIMO broadcast channels have been investigated quite extensively over the last years, there are still a lot of open questions that need to be resolved, both in theory and in practical implementation. For example, LTE offers the flexibility to adjust many transmission parameters, but it is not clear up to now how to exploit the available Degrees of Freedom (DoF) to achieve the optimum performance. Some recent theoretical results point out how to proceed in this matter, but practical results for LTE are still missing.
System level simulations
SL simulations focus more on network-related issues, such as resource allocation and scheduling, multi-user handling, mobility management, admission control, interference management],  and network planning optimization. On top of that, in a multi-user oriented system, such as LTE, it is not directly clear which figures of merit should be used to assess the performance of the system. The classical measures of (un)coded Bit Error Ratio (BER), (un)coded BLock Error Ratio (BLER), and throughput are not covering multi-user scenario properties. More comprehensive measures of the LTE performance are for example fairness, multi-user diversity, or DoF.  However, these theoretical concepts have to be mapped to performance values that can be evaluated by means of simulations.
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How 5G reduces data transmission latency

One of the essential requirements in 5G wireless systems is minimizing packet transmission latency for ultra-reliable and low latency (URLLC) services. One of the most prominent examples will be vehicle-to-everything (V2X) communications. V2X certainly includes reaching vehicles with broadband services, but latency isn’t an issue there. Low latency in cellular networks is a prerequisite for making autonomous vehicles safe. 

Autonomous vehicles will have to sense other vehicles, road conditions, pedestrians, and other obstacles. Often there will be environmental sensors to supplement this information; that data will frequently be available to autonomous vehicles via road side units (RSU) or other vehicles. Low-latency connections among these RSUs, the V2X application servers, and vehicle-based systems will lead to faster decision-making, which will lead to improved safety.

As an example, consider stopping distances. When a person operating a vehicle on a highway moving at 70 mph recognizes a danger, the traditional stopping distance is 96 meters, or 315 feet (Figure 1). Twenty-one meters of the total 96m is a thinking distance, based on a reaction time of 0.67s, the remaining 75m is actual braking distance. But with autonomous driving engaged, vehicles would recognize the dangerous situation earlier, the thinking distance would be reduced, and there would be more space for braking. The result will be a significant decrease in collision rates. 

Figure 1 Typical stopping distances. Source: UK Department for Transport

The V2X system assists vehicles to rapidly recognize the danger by alerting vehicles in vicinity of the hazardous situation, and the 1 millisecond (ms) end-to-end transmission latency requirement of 5G minimizes the reaction time of autonomous driving cars.

The existing LTE (long-term evolution – a 4G technology) system has a couple of fundamental limitations preventing it from supporting 1ms latency. The first obstacle is that the minimum size of a radio transport block is a subframe having 1ms length. This means a duration of 1ms is spent solely for transmitting the transport block via air interface, excluding processing time at devices and transmission latency in network. 

To reduce response time, 5G uses a scalable orthogonal frequency-division multiplexing (OFDM) framework with different numerologies. Within a 1ms time duration, six separate slot configurations are available, e.g. 1, 2, 4, 8, 16, and 32 slots. The minimum size of a transport block could be reduced to a minimum of 0.03125ms based on the new configuration as shown in Figure 2.


Figure 2 Example slot configuration of multiple types of numerologies (TTIs). Source: 3GPP

Another characteristic of LTE that makes it difficult to reduce latency is the radio resource allocation delay between a vehicle and base station. When a vehicle wants to transmit packets, a radio resource grant procedure precedes the packet transmission. To transmit a resource scheduling request and send packets on the scheduled resource, a vehicle needs at least 8ms. In LTE, the semi-persistent scheduling (SPS) feature was introduced for periodic data transmissions like voice over IP (VoIP) services. 

When a base station configures SPS radio resources, a mobile handset can employ the periodic resources, without an additional scheduling request procedure. When the device gets data to send in its buffer, it can transmit the data via the next periodic resource already configured.

However, the existing LTE SPS configuration is dedicated to a single device. If the device does not need periodic resources, for example transmitting data only when specific events occur, such as a collision warning, the SPS resources unemployed by the device are wasted. 

To reduce the waste of periodically allocated resources, 5G enables multiple devices to share the periodic resources, called a configured grant (Type 1). The configured grant is based on the LTE SPS feature. In Figure 3, the base station allocates the configured grant resources to multiple vehicles, and the vehicles randomly utilize the resources when they have data to transmit. By assigning the configured grant resources, the 5G network eliminates the packet transmission delay for a scheduling request procedure and increases the utilization ratio of allocated periodic radio resources.


Figure 3 Configured grant resources

Ofinno has developed a number of patented technologies regarding SPS and configured grant technologies. The technologies of the patents improve operation efficiency of the configured grant by proposing multiple SPS configurations, enhanced mobility mechanisms, carrier aggregation for V2X services, device capability information sharing, and power control methods. The multiple SPS configurations provide efficient resource utilization and reduce transmission latency with optimized resource configurations (e.g. periodicity and resource size) for different types of services. The enhanced mobility mechanisms enable reliable packet transmission during a handover procedure of V2X devices. The carrier aggregation for V2X services boosts up radio resource capacity with introduction of multiple cell cooperation for reliable V2X services.

 

Source: edn.com

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Introduction to Latency towards 5G

In developing wireless 5G standards, we have an opportunity to further reduce latency, the time delays, in future wireless networks.  In fact, there appears to be unanimous opinion that 5G standards should have less than 1 millisecond (msec) of latency.[1],[2],[3],[4] But why?

In considering results from neurology and studies of interactive games, and in considering the current state of network latency, we do not see compelling business requirements for lower latencies, except insofar as such improvements can also improve throughput and connection setup times. Support for high speed trains may also benefit from lower latencies.

Before discussing the motivation behind a latency requirement of ≤1 msec, let’s be clear on what we mean by latency. The various proposals for 5G are typically specific about the numerical goals for the standard but rarely specific about what the numbers really mean. Some talk of latency as End to End delay, or round trip times, transmit time interval (TTI), ping times, Radio Link Layer TX to ACK times, call setup time, etc.; but nearly all say “it” should be no more than 1 msec. To be specific:

 

  1. Transmit Time Interval (TTI):  The minimum length of time of a UE specific transmission.
    In the case of LTE, one sub frame is 1 msec long and consists of 2 time slots. This is the smallest scheduled time interval that can be allocated to a UE. Before one can start transmitting a burst of encoded and error protected data, one must have the complete transport block, which means that there is at least this much delay between getting the data from microphone or camera or other sensor and transmitting it. One can say that LTE has a 0.5 msec TTI.
    Large IP packets may need to be segmented in to multiple TTIs depending upon the coding and modulation schemes chosen to adapt to the channel quality. This segmentation can lead to a single IP packet being scheduled onto several time slots.
  2. HARQ processing time: There is a reasonable chance that a received transmission will be in error, typically assumed to be about 10%. When this happens, a Hybrid Automatic Retransmission reQuest is sent (HARQ) between the eNodeB and the User Equipment (UE). The latency of a wireless system needs to account for the processing time to decode and error check a transport block, send a retransmission request and expect one or more retransmissions. These retransmissions are one important source of jitter in the timing.
    In the case of LTE, the HARQ processing time delay is 4 subframes (4 msec) so a retransmission requires 7 msecs, with a chance of several more such requests depending upon interference and levels, signal strength and congestion. This is shown in the following figure. With TTI bundling of the sort used in VoLTE there is a 12 msec delay. LTE Timing DiagramFor TDD-LTE, the HARQ delay is 9 to 10 msec and 13 to 16 msec for for TTI bundling of the sort used with VoLTE.
  3. Frame size: The minimum time period between system transmissions from a radio that includes feedback from the other end of the link.
    As illustrated in the previous figure, in LTE, the frame is 10 msec long and is the periodicity of the Physical Broadcast Channel (PBCH) used for synchronization with the Master Information Block (MIB).  Note that ideally, when datagrams are small, and channel quality is good, UE to eNodeB to UE times can be as little as 5 msec, which is less than the frame sizes.[5] This is commonly misunderstood in discussions of latency; an acknowledged transmission can be faster than the frame interval.
  4. The Round Trip Time (RTT) typically refers to the “ping time” to send a short IP packet from the UE to a server in the Internet and receive a reply back. Because Ping time is easily measured from any smart phone, tablet or laptop, the press typically reports these ping times as latencies. These numbers are dominated by the network delays between the base station and the servers or other end points illustrated on the far right of the previous figure. The internet may introduce seconds of delays when connections go through satellite links or intercontinental routes.
  5. Discontinuous Reception – Receiving the Physical Downlink Control Channel every 1 msec to listen for pages from the network would waste battery capacity. Rather than reduce battery life so quickly, UEs use Discontinuous Reception (DRX) in which they skip many frames and only wake up every 32 frames (or so) to check for relevant downlink signals. This is not relevant when the UE is in actively connected mode (Cell_DCH), but it creates a long latency of many tens of msec for unscheduled messaging.[6]

These various measures of latency and communications delays have regularly improved over time as suggested in the comparative plot below. This shows minimum LTE ping times of 44 msec to the OOKLA “speedtest” server.  It shows the ping times for LTE 4G has a minimum round trip ping time of 32 and 44 msec (on AT&T and Verizon service, respectively) compared with 88 msec for UMTS HSPA 3G service on an iPhone 4 (AT&T). (The iPhone 4S measurements were all made at the same location and night while the others were measured in much more varied conditions.)

Ping Round Trip Times

The 32 msec minimum LTE ping time may appear at odds with the theoretical minimum of 5 msec round trip time discussed above, but the 5 msec figure was only for a UE transmission to be acknowledged from the eNodeB, while the 32 msec measured ping time was to a server located in the internet over 40 km away and with several intermediate nodes along the way. OpenSignal has reported LTE latency of 98 msec averaged over several operators.[7]

There are several reasons to try to reduce the TTI, frame, HARQ and setup times in making 5G. For example, reducing the TTI time slot interval directly reduces the feedback time, enabling smaller buffers and more efficient and timely feedback. But we should be clear that end to end times are determined primarily by network considerations, and that further improvements in the air interface will not help end to end delays improve substantially.

As an example, the very fastest fiber optic link between the Chicago and New York stock exchanges have been optimized with extravagant deployments of particularly straight paths to get to 13 msec round trip times. It turns out that the High Velocity traders on Wall Street want the fastest possible link from their computers to the trading computers on Wall Street.

One company, Spread Networks® offers a dedicated network connection from Chicago to NJ/NYC for this specific purpose.[8]

Chicago to NYC is about 1140 km in a straight line.  Light travels thru fiber at about 200 km per 1 ms – so light takes about 6.5 ms just to travel from Chicago to NYC, one way (in a straight line), or about 13 ms round trip.  So, given Spread Networks® report of taking about 14.5 ms, this means that there is an additional 1.5 ms for the signal to go thru the regenerators, computers, routers and other switching equipment, round trip. (Purpose built microwave links between Chicago and New York City claim to have reduced to the time to ~8.6 ms round trip, thanks to the fact that air has a higher refractive index than glass.[9] (The speed of light limit is 7.6 msec, so they have done an excellent job of reducing regeneration and error correction delays.)

From this extravagant system, we are lead to conclude that 82 miles or 132 km is as far as one could backhaul without incurring 1 msec of additional round trip delay.  So when 5G proponents talk of 1 msec E2E latencies, we are restricted to distances much less than 82 miles or the distance between New York City and Philadelphia, PA.

This suggests one approah to reduce End to End (E2E) latencies; by offloading local traffic at the base station. This would allow two interactive gamers or two vehicles that are within the same cell to communicate with sub frame time latencies. This would express local traffic without incurring the delays in the network to the right of the Service Gate Way (SGW) shown in the first figure.

Which Applications need low latencies?

Which applications, and what business cases, drive the need for low latencies?

A number of proponents have suggested that 5G will enable what is loosely called, “Tactile Networks.”[10], [11] This is to serve very responsive applications such as gaming and vehicle control systems.

However, we find from neurological studies that conduction velocities of nerves are on the order of a few inches per millisecond. To conduct pain 1 meter, from, say, fingertips to brainstem, takes 29 to 200 msec with the Aδ axons, as indicated in the following figure.  This is even without motor feedback or cognitive processing. [12] 

axion condution velocities

 

Once Electro Mechanical Delay (EMD) is considered, we see that there are tens of milliseconds of delay in even reflex responses. [13]

In interactive computer games, researchers tell us that in the most demanding games of First Person Player or Racing games, about 50 msec latencies are inconsequential.[14] One oft-cited article suggests that the threshold for first person shooter games and racing is 100 msec.[15] (Though a graphic shows some improvement in lap times for a racing game as the latency is decreased below 100 msec.)

It is worth remembering that the screen refresh rate in film is 24 fps or 41.66 msec, which the eye does not detect. That is to say, many displays would not even present a gamer with a new view of the racetrack more often than about every 20 msec. The European Broadcasting Union recommendation on Lip-Synch, the time delay between audio and video content, states that audio/video synch should be within +40 msec to -60msec  (audio before/after video), but are often off by 100 msec. This further supports the notion that the human nervous system is insensitive to the sort of latencies of tens of msec.

Remember how proud you were of yourself when you caught an object that had fallen from a tabletop? To drop 1 meter takes 250 msec, much longer than the 1 msec response times proposed to enable “tactile networks.”

 

Why might we need latencies under 1 millisecond?

Communications between autonomous automobiles is both local (likely the same cell) and potentially urgent.  However, even here we observe that at 55 MPH a car moves 1 inch in 1 msec. So latency in inter-car communications of even 10 msec corresponds to less than a foot or 25 cm. Air bags deploy in 15 to 30 msec.

As a result, the authors suggest that aside from research funding opportunities, very low latencies of ≤1 msec have not clear business drivers, with the exception of generally improving overall throughput and channel sensing at speeds corresponding to high-speed trains.  In such cases, and for these reasons alone, it appears that improvements to the latencies inherent in the air interface may be warranted, but otherwise the business imperatives are not apparent.

In fact, for sensor networks, and similar machine-to-machine communications, time diversity from repeated transmissions or HARQ may be more helpful to communicating high value bits through extended link budgets with penetration through walls and earth, than low latency. A delay of many seconds in communicating an alert of a flooded basement or a utility meter reading seems a valuable tradeoff in the interest of reliability and range.

 

 

Footnotes:

[1] IWPC white paper, Mobile Multi Gigabit (Mogig) Wireless Networks And Terminals – 5000x Working Group, April 2, 2014. http://iwpc.org/WhitePapers.aspx#5000x. METIS requirements, presentations by Samsung, Intel, Ericsson, 5GNow, etc. etc.

[2] Presentation by Howard Been, Jan 2014, Vision and Key Features for 5thGeneration (5G) Cellular. Available on-line at: http://cambridgewireless.co.uk/Presentation/RadioTech_30.01.14_HowardBenn.Samsung.pdf

[3] Ericsson white paper, “5G Radio Access, Challenges for 2020 and Beyond.” June 2013. Available at: http://www.ericsson.com/res/docs/whitepapers/wp-5g.pdf

[4] METIS Document Number: ICT-317669-METIS/D1.1, Scenarios, requirements and KPIs for 5G mobile and wireless system, April 29, 2013. Available on line at: https://www.metis2020.com/wp-content/uploads/deliverables/METIS_D1.1_v1.pdf

[5] Here we define latency as the time difference between the start of a transmission and the receipt of its acknowledgement from the other end of the radio link, as defined in the excellent paper, Blajić, Nogulić, and Družijanić, “Latency Improvements in 3G Long Term Evolution.” Mipro CTI, svibanj(2006), available on-line at: http://nashville.dyndns.org:800/WirelessDownloads/_lte/Core%20EPC%20and%20SAE/LatencyImprovementsInLTE.pdf

[6] Bontu, C.S.; Illidge, E., “DRX mechanism for power saving in LTE,” Communications Magazine, IEEE , vol.47, no.6, pp.48,55, June 2009. available on line at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5116800&isnumber=5116787

[7] Samuel Johnston, “LTE Latency: How does it compare to other technologies?” report of OpenSignal March 10, 2014. Available at: http://opensignal.com/blog/2014/03/10/lte-latency-how-does-it-compare-to-other-technologies/

[8] Spread Networks® Latencies for Ultra Low Latency Service Latency between Chicago – 350 E. Cermak and New Jersey Trading Venues

http://www.spreadnetworks.com/media/11244/wavelength_latencies_chicago_to_nj_12_2013a.pdf  and  http://spreadnetworks.com/products/ultra-low-latency-services/carteret-to-chicago-dark-fiber-–-1300-milliseconds-roundtrip/

[9] Jake Thomases, “Capital Markets to Embrace Microwaves for Data Feeds,” Source: Waters | 16 Aug 2013, available at: http://www.waterstechnology.com/waters/feature/2289570/capital-markets-to-embrace-microwaves-for-data-feeds

 [10] Gerhard Fettweis, “The Tactile Internet – Driving 5G,” ETSI Future Mobile Summit, Nov 21, 2013. available on line at: http://docbox.etsi.org/Workshop/2013/201311_FUTUREMOBILESUMMIT/11_TECHNICALUNIofDRESDEN_FETTWEIS.pdf

 [11] Gerhard Fettweis, “5G – What will it be: The Tactile Internet,” July 30, 2013, available at: http://icc2013.ieee-icc.org/speakers_17_198889650.pdf

 [12] Eric Chudler, private communications June 2014 and web on conduction velocities:  https://faculty.washington.edu/chudler/cv.html

 [13] ElectroMechanical Delays (EMD) of reflex responses (which do not go through the brain) are measured to be from 7 msec to 40.8msec (Zhou, Shi, Lawson, David, Morrison, William, “Electromechanical delay in isometric muscle contractions evoked by voluntary, reflex and electrical stimulation,” European Journal of Applied Physiology and Occupational Physiology, 1995, Volume 70, Issue 2, pp 138-145)

 [14] Claypool, Mark, and Kajal Claypool. “Latency can kill: precision and deadline in online games.” Proceedings of the first annual ACM SIGMM conference on Multimedia systems. ACM, 2010. http://dl.acm.org/citation.cfm?id=1730863

 [15] Claypool, & Claypool, “Latency and Player Actions in Online Games,” Communications of the ACM, Nov. 2006/ Vol. 49, No. 11, available at: http://web.cs.wpi.edu/~claypool/papers/precision-deadline/final.pdf

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5G new technology aspects

The total download capacity for a single 5G mobile cell must be at least 20Gbps, the International Telecommunication Union (ITU) has decided. In contrast, the peak data rate for current LTE cells is about 1Gbps. The incoming 5G standard must also support up to 1 million connected devices per square kilometre, and the standard will require carriers to have at least 100MHz of free spectrum, scaling up to 1GHz where feasible.
These requirements come from the ITU’s draft report on the technical requirements for IMT-2020 (aka 5G) radio interfaces, which was published Thursday. The document is technically just a draft at this point, but that’s underselling its significance: it will likely be approved and finalised in November this year, at which point work begins in earnest on building 5G tech.

I’ll pick out a few of the more interesting tidbits from the draft spec, but if you want to read the document yourself, don’t be scared: it’s surprisingly human-readable.

5G peak data rate
The specification calls for at least 20Gbps downlink and 10Gbps uplink per mobile base station. This is the total amount of traffic that can be handled by a single cell. In theory, fixed wireless broadband users might get speeds close to this with 5G, if they have a dedicated point-to-point connection. In reality, those 20 gigabits will be split between all of the users on the cell.
5G connection density
Speaking of users… 5G must support at least 1 million connected devices per square kilometre (0.38 square miles). This might sound like a lot (and it is), but it sounds like this is mostly for the Internet of Things, rather than super-dense cities. When every traffic light, parking space, and vehicle is 5G-enabled, you’ll start to hit that kind of connection density.
5G mobility
Similar to LTE and LTE-Advanced, the 5G spec calls for base stations that can support everything from 0km/h all the way up to “500km/h high speed vehicular” access (i.e. trains). The spec talks a bit about how different physical locations will need different cell setups: indoor and dense urban areas don’t need to worry about high-speed vehicular access, but rural areas need to support pedestrians, vehicular, and high-speed vehicular users.
5G energy efficiency
The 5G spec calls for radio interfaces that are energy efficient when under load, but also drop into a low energy mode quickly when not in use. To enable this, the control plane latency should ideally be as low as 10ms—as in, a 5G radio should switch from full-speed to battery-efficient states within 10ms.
5G latency

Under ideal circumstances, 5G networks should offer users a maximum latency of just 4ms, down from about 20ms on LTE cells. The 5G spec also calls for a latency of just 1ms for ultra-reliable low latency communications (URLLC).

5G spectral efficiency
It sounds like 5G’s peak spectral efficiency—how many bits can be carried through the air per hertz of spectrum—is very close to LTE-Advanced, at 30bits/Hz downlink and 15 bits/Hz uplink. These figures are assuming 8×4 MIMO (8 spatial layers down, 4 spatial layers up).
5G real-world data rate

Finally, despite the peak capacity of each 5G cell, the spec “only” calls for a per-user download speed of 100Mbps and upload speed of 50Mbps. These are pretty close to the speeds you might achieve on EE’s LTE-Advanced network, though with 5G it sounds like you will always get at least 100Mbps down, rather than on a good day, downhill, with the wind behind you.

The draft 5G spec also calls for increased reliability (i.e. packets should almost always get to the base station within 1ms), and the interruption time when moving between 5G cells should be 0ms—it must be instantaneous with no drop-outs.

The order of play for IMT-2020, aka the 5G spec.

The order of play for IMT-2020, aka the 5G spec.

The next step, as shown in the image above, is to turn the fluffy 5G draft spec into real technology. How will peak data rates of 20Gbps be achieved? What blocks of spectrum will 5G actually use? 100MHz of clear spectrum is quite hard to come by below 2.5GHz, but relatively easy above 6GHz. Will the connection density requirement force some compromises elsewhere in the spec? Who knows—we’ll find out in the next year or two, as telecoms and chip makers start developing draft 5G tech.

 

Source: arstechnica.com

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5G channel coding

Polar codes, a class of codes which allows to
1. attain the capacity of all symmetric memoryless channels (=those for which the
capacity is attained for a uniform input distribution),
2. with an encoding algorithm of complexity O(N log N) (N = code length),
3. with a decoding algorithm of complexity O(N log N).
This decoding algorithm borrows many ideas from the decoding algorithm used for
LDPC codes.

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Wireless Networking basic concepts and understanding

Introduction

As the basis for understanding the installation, operation, and troubleshooting of wireless LANs (WLANs), it is important that you have a good knowledge of how radio waves propagate through an environment. Every Wi-Fi deployment requires that the systems engineer understand the fundamentals of how radio waves move and react within the environment.

For example, in a WLAN, radio waves carry information over the air from one point to another. Along the way, the waves encounter various obstacles or obstructions that can impact range and performance, depending on the characteristics of the radio wave. In addition, regulatory rules govern the use and limitations of radio waves. This excerpt explains the fundamentals of radio waves so that you have a good basis for understanding the complexities of deploying WLANs.

Radio wave attributes

A radio wave is a type of electromagnetic signal designed to carry information through the air over relatively long distances. Sometimes radio waves are referred to as radio frequency (RF) signals. These signals oscillate at a very high frequency, which allows the waves to travel through the air similar to waves on an ocean. Radio waves have been in use for many years. They provide the means for carrying music to FM radios and video to televisions. In addition, radio waves are the primary means for carrying data over a wireless network. As shown in Figure 2-1 , a radio wave has amplitude, frequency, and phase elements. These attributes may be varied in time to represent information.

Amplitude
The amplitude of a radio wave indicates its strength. The measure for amplitude is generally power, which is analogous to the amount of effort a person needs to exert to ride a bicycle over a specific distance. Similarly, power in terms of electromagnetic signals represents the amount of energy necessary to push the signal over a particular distance. As the power increases, so does the range.
Radio waves have amplitudes with units of watts, which represent the amount of power in the signal. Watts have linear characteristics that follow mathematical relationships we are all very familiar with. For example, the result of doubling 10 milliwatts (mW) is 20 mW. We certainly do not need to do any serious number crunching to get that result.
As an alternative, it is possible to use dBm units (decibels referenced to 1 mW) to represent the amplitude of radio waves. The dBm is the amount of power in watts referenced to 1 mW. Zero (0) dBm equals 1 mW. By the way, the little m in dBm is a good reminder of the 1 mW reference. The dBm values are positive above 1 mW and negative below 1 mW. Beyond that, math with dBm values gets a bit harder. Refer to the section “RF Mathematics,” later in this chapter, to learn how to convert between watts and dBm units and understand why it is preferable to use dBm units.
Note: You can adjust the transmit power of most client cards and access points. For example, some access points allow you to set the transmit power in increments from –1 dBm (0.78 mW) up to 23 dBm (200 mW).

Frequency
The frequency of a radio wave is the number of times per second that the signal repeats itself. The unit for frequency is Hertz (Hz), which is actually the number of cycles occurring each second. In fact, an old convention for the unit for frequency is cycles per second (cps).
802.11 WLANs use radio waves having frequencies of 2.4 GHz and 5 GHz, which means that the signal includes 2,400,000,000 cycles per second and 5,000,000,000 cycles per second, respectively. Signals operating at these frequencies are too high for humans to hear and too low for humans to see. Thus, radio waves are not noticed by humans.
The frequency impacts the propagation of radio waves. Theoretically, higher-frequency signals propagate over a shorter range than lower-frequency signals. In practice, however, the range of different frequency signals might be the same, or higher-frequency signals might propagate farther than lower-frequency signals. For example, a 5-GHz signal transmitted at a higher transmit power might go farther than a 2.4-GHz signal transmitted at a lower power, especially if electrical noise in the area impacts the 5-GHz part of the radio spectrum less than the 2.4-GHz portion of the spectrum (which is generally the case).
Phase
The phase of a radio wave corresponds to how far the signal is offset from a reference point (such as a particular time or another signal). By convention, each cycle of the signal spans 360 degrees. For example, a signal might have a phase shift of 90 degrees, which means that the offset amount is one-quarter (90/360 = 1/4) of the signal.

RF System Components

Figure 2-2 illustrates a basic RF system that enables the propagation of radio waves. The transceiver and antenna can be integrated inside the client device or can be an external component. The transmission medium is primarily air, but there might be obstacles, such as walls and furniture.

RF Transceiver
A key component of a WLAN is the RF transceiver, which consists of a transmitter and a receiver. The transmitter transmits the radio wave on one end of the system (the “source”), and the receiver receives the radio wave on the other side (the “destination”) of the system. The transceiver is generally composed of hardware that is part of the wireless client radio device (sometimes referred to as a client card).
Figure 2-3 shows the basic components of a transmitter. A process known as modulation converts electrical digital signals that represent information (data bits, 1s and 0s) inside a computer into radio waves at the desired frequency, which propagate through the air medium. Refer to the section “RF Modulation” for details on how modulation works. The amplifier increases the amplitude of the radio wave signal to a desired transmit power prior to being fed to the antenna and propagating through the transmission medium (consisting primarily of air in addition to obstacles, such as walls, ceilings, chairs, and so on).

At the destination, a receiver (see Figure 2-4 ) detects the relatively weak RF signal and demodulates it into data types applicable to the destination computer. The radio wave at the receiver must have amplitude that is above the receiver sensitivity of the receiver; otherwise, the receiver will not be able to “interpret” the signal, or decode it. The minimum receiver sensitivity depends on the data rate. For example, say that the receiver sensitivity of an access point is –69 dBm for 300 Mbps (802.11n) and –90 dBm for 1 Mbps (802.11b). The amplitude of the radio wave at the receiver of this access point must be above –69 dBm for 300 Mbps or above –90 dBm for 1 Mbps before the receiver will be able to decode the signal.

RF Modulation
RF modulation transforms digital data, such as binary 1s and 0s representing an e-mail message, from the network into an RF signal suitable for transmission through the air. This involves converting the digital signal representing the data into an analog signal. As part of this process, modulation superimposes the digital data signal onto a carrier signal, which is a radio wave having a specific frequency. In effect, the data rides on top of the carrier. To represent the data, the modulation signal varies the carrier signal in a manner that represents the data.
Modulation is necessary because it is not practical to transmit data in its native form. For example, say that Kimberlyn wants to transmit her voice wirelessly from Dayton to Cincinnati, which is about 65 miles. One approach is for Kimberlyn to use a really high-powered audio amplifier system to boost her voice enough to be heard over a 65-mile range. The problem with this, of course, is that the intense volume would probably deafen everyone in Dayton and all the communities between Dayton and Cincinnati. Instead, a better approach is to modulate Kimberlyn’s voice with a radio wave or light carrier signal that’s out of range of human hearing and suitable for propagation through the air. The data signal can vary the amplitude, frequency, or phase of the carrier signal, and amplification of the carrier will not bother humans because it is well beyond the hearing range.
The latter is precisely what modulation does. A modulator mixes the source data signal with a carrier signal. In addition, the transmitter couples the resulting modulated and amplified signals to an antenna, which is designed to interface the signal to the air. The modulated signal then departs the antenna and propagates through the air. The receiving station antenna couples the modulated signal into a demodulator, which derives the data signal from the signal carrier.
Amplitude-Shift Keying
One of the simplest forms of modulation is amplitude modulation (sometimes referred to as amplitude-shift keying), which varies the amplitude of a signal to represent data. Figure 2-5 illustrates this concept. Frequency-shift keying (FSK) is common for lightbased systems whereby the presence of a 1 data bit turns the light on and the presence of a 0 bit turns the light off. Actual light signal codes are more complex, but the main idea is to turn the light on and off to send the data. This is similar to giving flashlights to two people in a dark room and having them communicate with each other by flicking the flashlights on and off to send coded information.
Amplitude modulation alone does not work very well with RF systems because there are signals (noise) present inside buildings and outdoors that alter the amplitude of the radio wave, which causes the receiver to demodulate the signal incorrectly. These noise signals can cause the signal amplitude to be artificially high for a period of time; for example, the receiver would demodulate the signal into something that does not represent what was intended (for example, 10000001101101 would become 10111101101101). To combat impacts from noise, modulation for RF systems is more complex than using only amplitude modulation.

Frequency-Shift Keying
FSK makes slight changes to the frequency of the carrier signal to represent data in a manner that’s suitable for propagation through the air at low to moderate data rates. For example, as shown in Figure 2-6 , modulation can represent a 1 or 0 data bit with either a positive or negative shift in frequency of the carrier. If the shift in frequency is negative—that is, a shift of the carrier to a lower frequency—the result is a logic 0. The receiver can detect this shift in frequency and demodulate the results as a 0 data bit. As a result, FSK avoids the impacts of common noise that exhibits shifts in amplitude.

Phase-Shift Keying
Some systems use phase-shift keying (PSK), which is similar to FSK, for modulation purposes for low to moderate data rates. With PSK, data causes changes in the signal’s phase, while the frequency remains constant. The phase shift, as Figure 2-7 depicts, can correspond to a specific positive or negative amount relative to a reference. A receiver can detect these phase shifts and realize the corresponding data bits. As with FSK, PSK is mostly immune to common noise that is based on shifts in amplitude.

Quadrature Amplitude Modulation
Quadrature amplitude modulation (QAM) causes both the amplitude and phase of the carrier to change to represent patterns of data, often referred to as symbols. The advantage of QAM is the capability of representing large groups of bits as a single amplitude and phase combination. In fact, some QAM-based systems, for example, make use of 64 different phase and amplitude combinations, resulting in the representation of 6 data bits per symbol. Higher-order combinations of phase and amplitude in QAM make it possible for standards such as 802.11n and 802.11ac to support higher data rates.
Spread Spectrum
After modulating the digital signal into an analog carrier signal using FSK, PSK, or QAM, some WLAN transceivers spread the modulated carrier over a wider spectrum to comply with regulatory rules. This process, called spread spectrum , significantly reduces the possibility of outward and inward interference. As a result, regulatory bodies generally do not require users of spread spectrum systems to obtain licenses. Spread spectrum, developed originally by the military, spreads a signal’s power over a wide band of frequencies (see Figure 2-8 ).

Spread spectrum radio components use either direct sequence or frequency hopping for spreading the signal. Direct sequence modulates a radio carrier by a digital code with a bit rate much higher than the information signal bandwidth. Figure 2-9 is a hypothetical example of direct sequence that represents the transmission of three data bits (101) serially in time. The actual transmission is based on a different code word that represents each type of data bit (1 and 0). As shown in the figure, when sending a data bit 1, the radio sends the code word 00010011100 to represent the data bit. Similarly, when sending a data bit 0, the radio sends the code word 11101100011. The increase in the number of bits sent that represents the data effectively spreads the signal across a wider portion of the frequency spectrum.

Frequency hopping uses a different technique to spread the signal by quickly hopping the radio carrier from one frequency to another within a specific range. Figure 2-10 illustrates this concept. The boxes labelled A, B, C, D, and E in the figure represent bursts of data that are sent at different times and frequencies. This also effectively spreads the signal across a wider part of the spectrum.

Orthogonal Frequency-Division Multiplexing
Instead of using spread spectrum, higher-speed WLANs make use of orthogonal frequency- division multiplexing (OFDM). OFDM divides a signal modulated with FSK, PSK, or QAM across multiple subcarriers occupying a specific channel (see Figure 2-11 ). OFDM is extremely efficient, which enables it to provide the higher data rates and minimize multipath propagation problems. OFDM has also been around for a while, supporting the global standard for asymmetric digital subscriber line (ADSL), a high-speed wired telephony standard.

Bandwidth

Bandwidth is measured in Hz. It describes the frequency band that a communication channel is able to transmit with low loss.

Typically we talk about a 3-dB bandwidth, meaning the range of frequencies a channel can transmit with less than 3 dB of loss. For a baseband system, the bandwidth extends from 0 Hz to a frequency which we call the bandwidth. For a modulated system if the carrier is atf0, then the transmission band would be from 

f0−B/2Also, outside of information theory, the term bandwidth may be used more broadly as a synonym for bit rate, or for data processing capacity, but when the units are Hz, we know we’re talking about the analogue bandwidth of a signal path of some kind.

Baud

Baud is the number of symbols transferred per second on the channel.

Bit rate

Bit rate indicates the amount of information transferred on a channel and is measured in bits per second or bps. Bit rate is different from baud if more than one bit is transferred per symbol. For example, in a 4-level amplitude modulation scheme, each symbol can encode 2 bits of information. Alternately, for example, when an error-correcting code is used, the bit rate can be less than the baud rate, as a larger number of symbols are used to convey a smaller number of bits of independent information.

The Shannon Theorem shows how bit rate is limited by bandwidth and the signal-to-noise ratio of the channel: 

where C is the capacity (maximum bit rate of the channel), B is the bandwidth of the channel, and SNR is the signal to noise ratio.

The relationship between Data transmission and Hz
Hz and bps are both a simple distinction and a complicated one. Simply, Hz applies to a clock frequency that is used to modulate the electrical signal on the transmission media, for instant air, wire. The higher the rate of modulation (Hz), the more information that can be transmitted per second. bps is typically different from the modulation rate and is primarily important with respect to data transfer rates. However, Shannon criterion states that you cannot transmit valid binary data at more than 1/2 the frequency of the transmission frequency (i.e. 1Hz=2b). The Bytes/Second, or Bytes/Minute or whatever else are just conversion issues and are meaningless to what the difference is between Hz and bps. The Shannon criterion is a huge issue and is the cornerstone of modern communication systems.
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Frame Error Rate vs Bit Error Rate

There are multiple ways in which the quality of networking products can be assessed. Two
clearly defined techniques are the measurement of bit error rate (BER) and frame error rate
(FER). Many networking products are specified with the bit error rate that they achieve or
support. BER is simply the ratio of bits that have been incorrectly received to the total number
of bits sent. The test is performed by sending strings of pseudo-randomly generated bits
through the device.

Frame error rate (FER) is a better test for two reasons:

  1. In real-world Ethernet networks, the basic data unit is a frame, a collection of bits arranged in a format consistent with the Ethernet standard. A frame can contain between 512 and 12,144 bits per the Ethernet standard. If a switch or a NIC receives a frame with one or many incorrectly transmitted bits, the complete frame will be discarded. The degradation of network performance due to dropped frames is the same for one or many bit errors within a frame. BER does not account for this fact.
  2. FER testing takes longer to complete. Berk-Tek performs FER testing for a minimum of one hour per test, whereas a BER test would
    take about two (2) minutes. This increased test time is significant because it allows the hardware and cabling to reach operating
    temperatures. The performance of networking products decreases as the temperature increases. Robust performance is, therefore, better verified during longer tests that allow for transceivers, switches, cabling, etc., to reach their true operating temperature.

Source: www.berktek.us

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Phones support 5G new technology

5th generation mobile networks or 5th generation wireless systems, in short, is known as 5G. It is the latest proposed telecommunications standard after 4G, 3G and 2G. The mobile data world is now fully equipped with 4G LTE networks. Recently, after the introduction of Reliance Jio network in India, the country has got a huge 4G network boost and is also ready for the next chapter.

5G network is the next chapter in the telecommunications standard, which will make our smartphones even more fast and powerful. Companies such as Qualcomm, Huawei and Nokia are working very hard to shape the standards of 5G. Today, we will look at the best 5G smartphones available in the world. Actually, there are upcoming smartphones that will get launched in the first half of 2018. However, before checking these best 5G devices, let’s have a look at the characteristics of 5G network.
First of all, let’s find out what is 5G? It is an upcoming telecom network system which will have much higher speeds and capacity along with much lower latency, compared to existing cellular systems. The technologies which are going to be used in 5G are still being defined. Mostly, 5G networks will be using a type of encoding called OFDM, similar to the one used in 4G LTE. 5G networks will be much smaller and smarter, compared to any previous systems. According to reports, the standard bodies are aiming at 20Gbps speeds at 1ms latency.
5G will not only enable better usage of smartphones, but it will also start the era of driverless smart cars and smart homes. In the smartphone sector, the biggest change with the introduction of 5G is expected in the field of AR (Augmented Reality) and VR (Virtual Reality). In USA, AT&T and Verizon is expected to launch pre-5G in 2017 but official 5G will get launched in 2018 and will go mainstream by 2019. Now, lets check out the upcoming 5G devices below.

Take a look at the Best 5G Smartphones (2018)

1.SAMSUNG GALAXY X

Samsung Galaxy X
Samsung keeps its engine running by producing trendy styles and displays like Edge, but it’s been circulating that its newest project Galaxy X (believed to be a part of Project Valley) will highlight a foldable display.
Apparently, this smartphone will have hinged second OLED panels that might ditch the bezels to achieve a full-screen look. This phone turns into a tablet with a 7-inch display when not folded. This is what makes it one of the most awaited phones to watch out for.
This is projected to be released during the second half of 2017, from July to September. Since it is supposed to be a test run, only 100,000 will be offered to South Korea. However, US, Poland, and the UK will also have their share.
Once these prototypes are released, the mobile giant will begin observing their performance. A consumer version will be released eventually. So be sure to check out this top choice as part of the most awaited phones to watch out for.
Digital Trends also reported that the official version might be launched at the Mobile World Congress in February 2018. However, a similar report said that the release is on 2019 due to Samsung’s desire to see an efficient performance first. Samsung is also planning on releasing two models, in which one has a 5-inch screen, but turns into an 8-inch display when it is rolled out.
Specs:
  • 4K Display
  • Dual camera
  • OLED display with 1080p
  • Arms control (automated)
  • 386ppi

2. Nokia 9

Nokia 9, an upcoming flagship smartphone of 2017, is also expected to support 5G network. This is because even Nokia is working very hard in defining the 5G network.
The Nokia 9 will be featuring a 5.3-inch Quad HD AMOLED display and Snapdragon 835 octa-core processor. There will be three RAM variants as per reports – 4GB/6GB/8GB.
In the camera department, we are expecting dual camera system consisting of two 13 megapixel sensors. It will be a 5G device or not remains to be seen but 4G VoLTE support will certainly be included.

3. Nokia P

Upcoming Phones - Nokia P
Nokia is said to come with an excellent line of mobiles after the company’s takeover. The upcoming series of phones is priced differently, but a model that falls in the premium category is Nokia P.
Launch date
The expected launch date of the mobile is 16th April 2017, a date that is subject to change.

Price

The planned cost of the cell phone is Rs. 42,999, which is also subject to change.

Features

This phone will only be available in black color and will not come in a metal body. The category that it will fall into is both smartphone and phablet, so you can have an idea of the size of the phone.
The phone will only be able to support a dual Nano SIM. It does not have a fingerprint scanner and neither is it waterproof. The network backed by this phone is LTE + LTE. The operating system is the latest model available in mobile phones: Android v7.0 Nougat.

Conclusion

Though it may feel like the phone does not come with too many features, there is a lot more that it does support. For example, it has a 64 GB internal storage and a 23 MP rear camera.

4. MI 8

Mi 8
Mi 8 smartphone was launched in May 2018. The phone comes with a 6.21-inch touchscreen display with a resolution of 1080 pixels by 2248 pixels at a PPI of 402 pixels per inch.
The Mi 8 is powered by octa-core processor and it comes with 6GB of RAM. The phone packs 64GB of internal storage. As far as the cameras are concerned, the Mi 8 packs a 12-megapixel primary camera on the rear and a 20-megapixel front shooter for selfies.
The Mi 8 runs Android Oreo and is powered by a 3400mAh. It measures 154.90 x 74.80 x 7.60 (height x width x thickness) and weighs 175.00 grams.
The Mi 8 is a dual SIM (GSM and GSM) smartphone that accepts Nano-SIM and Nano-SIM. Connectivity options include Wi-Fi, GPS, Bluetooth, NFC, USB OTG, 3G , 4G (with support for Band 40 used by some LTE networks in India) and probably 5G . Sensors on the phone include Compass/ Magnetometer, Proximity sensor, Accelerometer, Ambient light sensor, Gyroscope and Barometer.

5. NOKIA PHOENIX

 Related image

The Nokia Phoenix mobile features a 5.7″ (14.48 cm) display with a screen resolution of 1080 x 2160 pixels and runs on Android v8.0 (Oreo) operating system. The device is powered by Octa core (2.2 GHz, Dual core, Kryo 360 + 1.7 GHz, Quad core, Kryo 360) processor paired with 4 GB of RAM. As far as the battery is concerned it has 3000 mAh. Over that, as far as the rear camera is concerned this mobile has a 13 MP camera . Other sensors include Light sensor, Proximity sensor, Accelerometer, Compass, Gyroscope. So, does it have a fingerprint sensor? Yes, it does. For graphical performance that can make games run smoothly, this phone has got a Adreno 616 GPU. On board storage is at 64 GB with the option to expand the memory by Yes Up to 256 GB.

6. LG G7

LG G7, the successor of the G6 and G6+, is expected to launch at MWC in Barcelona in March 2018. According to reports, all the major flagship smartphones of 2018 will support 5G network and thus the G7 will be one of the best mobiles as well.
It will sport a 5.8-inch Quad HD+ display, which will be powered by Snapdragon 845 processor. For multitasking and storage, the LG G7 will have 6GB RAM and 128GB ROM. It will run on LG UX 7.0 based on Android 8.0 Oreo OS.
In the camera department, we can expect a 16 megapixel primary rear camera along with a 13 megapixel secondary rear camera.

7. HTC U12

HTC U12 will be launched at MWC 2018 in Barcelona in March. Like other flagship phones of 2018, the U12 is also expected to support the 5G network. It will feature a 5.8-inch Quad HD+ display, that will run on HTC Sense UI based on Android 8.0 Oreo OS.
This smartphone will be powered by Snapdragon 845 processor and 8GB RAM. It will also be IP68 certified and pack in a 3200mAh battery with support for wireless and fast charging.
In the camera department, we will get dual 12 megapixel rear cameras along with a 16 megapixel selfie shooter.

8. Xiaomi Mi 7

Xiaomi Mi 7, the flagship smartphone of 2018 is expected to launch in March. Being one of the smartphones, it will also support 4G VoLTE and other networks.
Other expected features include a 5.7-inch Quad HD+ display, Snapdragon 845 octa-core processor and 8GB RAM. It will run on MIUI 9 based on Android 8.0 Oreo OS. We are expecting a vertical dual camera setup at the back, just like the iPhone 8.
The vertical camera design is specifically made for VR and AR. It will have a glass and metal finish along with water and dust resistant body.

9. Huawei P11 / P11 Plus

Huawei P11 and P11 Plus, the next set of flagship smartphones, will get launched at MWC in March 2018. Since Huawei will be a major contributor in laying down the framework of 5G network, these will be 5G smartphones for sure, if the network doesn’t get delayed beyond 2018.
The P11 will sport a 5.2-inch Quad HD display whereas the P11 Plus will rock a 5.7-inch Quad HD+ display. These will be powered by Kirin 970 octa-core processor and 6GB of RAM. They will run on EMUI 6.0 based on Android 8.0 Oreo OS.
There will be a 20 megapixel primary camera along with a 12 megapixel secondary camera at the back in both the phones.

10. Asus Zenfone 5Z

Asus Zenfone 5Z, one of the best upcoming flagship smartphones of 2018 is expected to launch in June. If all other flagship smartphones get 5G connectivity, then Asus Zenfone 5Z will also be a 5G mobile phone.
It will rock a 5.8-inch Quad HD+ bezel-less Infinity display which will get powered by the Snapdragon 845 processor and 6GB RAM. If Asus Zenfone 5Z goes crazy, we can even see 10GB or 12GB RAM in the upcoming Asus Zenfone 5Z smartphone.

It will obviously come with dual rear cameras. The smartphone will run on Oxygen OS based on Android 8.0 Oreo OS out of the box.

We hope that you have liked our list of best 5G smartphones. The 5G network will supposedly be launching in 2018 and thus we are expecting all the major flagship smartphones to support the latest standard. If the 5G rollout gets delayed to 2019, then the next set of flagship smartphones will definitely support 5G. We will keep on updating the article whenever we get any developments on 5G. Do share this article for spreading awareness about the next big thing.

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What is the best simulation for 5G Wireless Networks?

From Manish Nair point of view the best simulation for 5G Wireless Networks for PHY Layer is Matlab and Simulink.

Matlab 2017 under academic license from MathWorks has the latest and greatest 5G toolbox, and is a great resource.

  • MAC-PHY Split and Protocol Stack

Open Air Interface (OAI) software libraries.[1]

The MAC-PHY split is implemented as an amendment to OAI5G source code. The OAI source code itself is split into two projects: OAI Radio Access Network (OAI-RAN) and OAI Core Network (OAI-CN).

OAI-RAN code is available on GitLab, and is distributed under OAI 5G public license.[2]

OAI-CN project implements 4G LTE Evolved Packet Core (EPC) and 5G Core Network. The code repository is on GitHub, and licensed by Apache.[3] [4]

  • Traffic, Scheduling and Queueing

IEEE 802.1 Qbv.[5]

This is the standard for Local and Metropolitan Area Networks, MAC Bridges and Virtual Bridged Local Area Network (VB-LAN) Enhancement for scheduled traffic.

Codes and specs can be found on the links in the reference.

  • Transport Networks

These are carrier specific. Open source code repositories are not available.

Footnotes

[1] 5G software alliance for democratising wireless innovation

[2] oai / openairinterface5G

[3] OpenAirInterface Software Alliance

[4] http://www.apache.org/licenses/L…

[5] 802.1Qbv – Enhancements for Scheduled Traffic

 

Answered by: Manish Nair, former Senior Engineer III Power Amplifier & RF HW Apps at Qualcomm

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